Generally, one of the driving factors in the design of modern electronics is the amount of computing power and storage that can be shoehorned into a given space. The well-known Moore's law states that the number of transistors on a given device will roughly double every eighteen months. In order to compress more processing power into ever smaller packages, transistor sizes have been reduced to the point where the ability to further shrink transistor sizes has been limited by the physical properties of the materials and processes. The use of field effect transistors (FETs) is common in large scale integrated circuits. Metal gates separated from a semiconductor substrate by an oxide are commonly used in FETs, but high-K films and gate stacks are increasingly replacing oxide dielectrics and metal gate electrodes in FETs. High-K materials may permit greater capacitance across the gate while reducing the leakage current associated with ultra-thin oxide insulators, permitting circuits with lower power usage.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale. For clarity non-essential reference numbers are left out of individual figures where possible.